Electrical control means for liquid fuel burning apparatus



Patented Sept. l5, 1953 ELECTRICAL CONTROL MEANS FOR LIQUID FUEL BURNINGAPPARATUS Allen E. Cleveland, Detroit, Mich., assignor to PerfectionStove Company, Cleveland, Ohio, a

corporation of Ohio Application September 8, 1948, Serial No. 48,312

9 Claims. l

This invention relates to the class of electrical control systems forcombustion devices and has particular, though not exclusive, utility asa means for automatically effecting a series of operations in responseto certain conditions occurring in the functioning of a combustiondevice.

For the purpose of the present disclosure and explanation, the inventionis shown and described herein in connection with an engine heatingapparatus incorporating a liquid fuel combustion device that forms thesubject matter of the copending application of Marc Resell, Serial No.674,012, iiled June 3, 1946, now Patent No. 2,509,399, dated May 30,1950, the present invention embracing improvements in the circuits of anelectrical control system for such a heating apparatus--a somewhatsimilar control system constituting the subject matter of my copendingapplication Serial No. 719,374, filed December 31, 1946, now Patent No.2,500,663, dated March 14, 1950. The present, as well as my earlierinvention just referred to, has special application to combustiondevices wherein an electrical igniting element is employed to initiatecombustion, and some means is desirably ineluded or required todeenergize said igniting element upon the attainment of propercombustion within the device.

lIhe primary object of my invention is the i),

provision of an electrical control system for heating apparatusincorporating a liquid fuel combustion device, and by means of whichsystem a complete cycle of operation is automatically accomplished whichincludes a starting or igniting phase, a so-called operating phase, anda shut-down phase, and wherein there is a safety feature thateffectively protects the heating apparatus and the various parts of thesystem from damage in case of failure of combustion during saidoperating phase, as well as during starting phase.

Other objects and advantages will appear as this description proceeds,in the course of which reference is made to the accompanying drawingwherein the figure is a diagrammatic representation of my improvedelectrical control system in operative association with a heatingapparatus of the liquid fuel combustion type equipped with a fuel pumpand a combustion air fan, said apparatus being shown in central verticalsection.

The heating apparatus is designated, generally, by the reference letterH. It includes a heat exchanger h in the form of an annular 2 liquidcirculating element having a central ue and the usual inlet and outletconnections h2 and h3, respectively. Said exchanger occupies acombustion chamber provided by the upper portion of a casing h4.Situated in the lower portion of said casing is a combustion device11,5, shown as a burner bowl that is arranged to discharge its productsupwardly into the combustion chamber and through the heat exchanger h.Interior parts of the apparatus are so shaped an-d related and so joinedto the casing as to set off within the latter a combustion air space h6to which air is supplied by an air impeller or blower F, hereinaftercalled the combustion fan, and which is driven by an electric motor f.

The combustion device is equipped with an electrical igniter hl, theterminals of which are designated ha and hf.

Liquid fuel is Supplied to the combustion device by a pump P, desirablyof the kind known to the trade as an autopulse pump and which isactuated by electromagnetic means, such as a solenoid, the winding ofwhich is indicated diagrammatically in dotted lines at p3. The outlet ofthe pump has communication with the combustion device through a pipe p',and receives fuel from a suitable source (not shown) through a pipe p2that has connection with the inlet of the pump.

A so-called control head or unit C surmounts the heater casing h4 and itis shown as comprising an inverted cup-like shell c', havingsubstantially the same cross sectional size and shape, or diameter, asthe casing h4 and it is slightly enlarged at its open end and istelescoped over the top of the casing to which it is secured by aSuitable number of screws c3. An outlet for the products of combustionis provided by an elbow c4 which has the end 0f its vertical branchextended into the ue of the heat exchanger h', while its horizontalbranch is projected through an opening in the peripheral wall of theshell c', the elbow and shell being welded together about said openingso as to make a rigid structure of two parts. The outer end of thehorizontal branch of the elbow is equipped with a clamp ci5 by which aflexible conduit or other type of iiue may be fastened to the elementfor carrying oil the products.

l'astened to the side of the shell c opposite that through which thehorizontal branch of the elbow c4 projects, is a bracket c" thatsupports a switch c8 of a type known as a Micro switch, althoughswitches of other suitable types may be substituted. The Micro switchincludes a leaf 3 spring conducting element C that is suitably fastenedat its upper end to a part of the switch casing C11, and its oppositeend swings between and alternately engages contacts C14 and C15. Theconducting element C10, by reason of its normal shape and inherentresiliency is biased toward and (if not otherwise influenced) held inengagement with the Contact C15; and it is adapted to be swung intoengagement with the Contact C14 by movement of a plunger C10 that isguided within a bore of the casing C11 and has a head that engages theConducting element near the fixed end of the latter, wherefore a veryslight movement of the plunger is required for swinging the conductingelement from the Contact C15 to the Contact C14.

The outer end of the plunger C10 is engaged by a lever C18 that ispivoted on a pin C19, supported by and between the sides of the bracketC1. A relatively short distance above the pivotal axis of the lever C10;compared to the distance between said axis and the point of Contactbetween the lever and the thrust pin C10, said lever is provided with anopening within which is guided the head of an adjusting screw C20, saidheadv and opening being shapedI to prevent turning of the former within`the latter. A nut C21 is threaded on the screw C and bears against thelever C10. Fastened tothev head of the adjusting screw C20, as by havingits encl brazed within an axial bore of the head, is one end of athermostatic tension element C24, This element, in the presentembodiment, consists of a wire of heatv resistant thermosensitive metal,and its end opposite the screw C20 is projected through a hole in thebottom of theV horizontal branch of the elbow C4 a short distanceoutwardlyy beyond the plane of the wall through which said elbowprojects and is turned back and welded to said wall immediately belowsaid branch. The member c and elbow c4 have apertures that are inalignment with the hole in the bottom` of the branch c4 through whichthe fixed end of the element C24 passes and the connection between theopposite end of said element and the screw C20 for the accommodation ofsaid element. When relatively cool, as when subjected to atmospheric orambient temperature, the ther,- mostatic tension element is suiiciently'taut to hold the lever C18 in a position which, through the-interventionof the plunger C10, will maintain the conducting element C10 of theMicro switch C11-in engagement with the contact C14,v as illustrated inthe drawing. When subjected to the temperature ofthe hot products ofcombustion that rise fromv the combustion device h5 through the heatexchanger h and escape through the elbow C4, said element will expandand relax its tension, allowing the conducting element C10 of the Microswitch to swing into engagement with theY Contact C15. Obviously (allother factors being constant), the time element involved in thisoperation may be Varied by changing the tension of the element C24, andthis s accomplished by adjusting the nut C21 along the screw C20. to-theupper end of the bracket c7 and is held thereto, and to the member C',by screws C28;

By reason ofthe fact that the functioning of the. control head isdependent entirely upon the linear expansion and contractionr of thethermo- Static tension element, and in viewl of the relatively smallcrosssectional area of said element, which causes it to absorb and giveup heat at a very rapid rate, the control head is quick and To protectthese parts, a cap C27'is applied lOV accurate in operation. In otherwords, it responds quickly when subjected to the exact temperature valueat which it .is set to shift the conducting element of the switch c8from one contact to the other.

I shall now proceed to describe the other electrical devices andcircuits represented diagrammatically in the drawing, and which, withthe beforementioned parts incorporated in the control head, constitutethe electrical control system of my invention by which is automaticallyaccomplished a series of operations in orderly sequence, inaugurated bythe lighting of the combustion device.

Briefly, the control system embraces a comparatively low resistance maincircuit, shown in the drawing in relatively heavy lines. This maincircuit includes a source B of electric current, represented as abattery; an overload cutout thermo-switch O (which may be any of thewell known varieties); the conducting element C10 of the switch C8 thatis incorporated in the control head C, and the Contact C14 thereof;contacts 2| and 20 of a voltage relay V2; a high current relay A,illustrated diagrammatically as a solenoid; the resistance heating coilt of a time-temperature cutout switch T (which involves, also, athermosensitive element t2, shown as a bimetal strip, andY which is incircuit closing position when cold,I as indicated in the drawing), andthe electrical igniter h1 ofv the combustion device h5. The conductorswhich-y with the foregoing electrical devices, make up the main circuit,will be presently introduced by reference characters.

Branching from said main circuit is an auxiliary one including a switchS that is in series with a thermostat R, as will hereinafter more fullyappear. The thermostat R is subjected to the temperature that is to be,controlled. Said auxiliary circuit also includes a Voltage relay V. Thisvoltage relay acts, when energized, to close two circuits. The rst ofsaid circuits includes the previously mentioned voltage relay V2 (which,

.. as will presently appear, controls the main circuit), and the secondof said circuits includes a voltage relay V4, the latter, upon beingener.- gized, closing a circuit through the thermosensitive element t2of the beforementioned timetemperature cutout switch T, as well' asthrough the winding p2 of the pump actuating electromagnetic meanspreviously referred to.

The two circuits last referred to eifect a cycle of operation of thecombustion device which includes a starting phase and a so-called normaloperating phase. I shall'rst describe the circuit responsible for thestarting phase, and therefore termed the starting circuit. Preliminaryto this, however, I shall complete the main and auxiliary circuits byintroducing the conductors thereof.

One terminal of the battery B isr grounded through a conductor l, whilethe other terminal thereof is connected, through a conductor 2, to aresistance heater o that forms a part of the overload cutout switch Oand is in a position to heat the thermosensitive element o2 (shown as abimetal strip) thereof; Said element o2 is normally in circuit closingposition, as when cold; as

indicated-in-the drawing. When said element o2 is heated and warpstocircuit opening position, it is held in such position, as by a latcho3, until manually released. A conductor 3 leads from the other side ofthe said overload cutout switch to a junction represented at 4. Fromthis junction a conductor leads to one side of the switch S, while theother side of said switch is connected, through a conductor 6, to thethermosensitive element of the thermostatic switch R. A contact r', intoengagement with which the thermosensitive element of the switch swingswhen subjected to a sufficiently low temperature, has connection,through a conductor l, with the coil of the relay V which is groundedthrough a conductor B.

It is evident from what has so far been said that when the switch S isclosed, and it is assumed that the overload switch O` and thethermostatic switch R are closed, that current will ow from the batterythrough the switch O, conductors 3 and 5, switch S, conductor 6,thermostatic switch R, conductor l, the coil of the relay V andconductor 8 to the ground. Upon energization of the relay V', a switchelement Iii, that is swung from normal to circuit closing position bythe armature of the relay, bridges contacts Il and I2, resulting in theclosing of the two circuits previously referred to, one as the startingcircuit, and which will presently be described. A part of the currentsupplied by the battery passes the junction 4 and continues through aconductor I3, past a junction I4, and via a conductor I5 to theconducting element 010 of the switch C8 that is incorporated in thecontrol head C.

During the starting phase of the operation, which is at present underconsideration, the thermostatic tension element C24 of the control headis cold, so to speak, and, therefore sufficiently taut to act, throughthe lever C18 and plunger C16, to hold the conducting element c1 of theswitch c8 against the contact C14. Consequently current will continue onthrough a conductor it, past a junction I'I, to the coil of the relayV2, and thence through a conductor I8 to the previously mentionedContact I I of the relay V. As will be remembered, this relay V haspreviously been energized to swing the switch element IEB intoengagement with the contacts II and I2, Wherefore the current owingthrough the circuit last W described, involving the conductor I8 and theContact Il, taking the course of least resistance will be groundedthrough a conductor I9. Energization of the relay V2 causes the switchelement 20 thereof to engage a contact 2| that is included in thecircuit that branches off from the junction Il of the previouslydescribed circuit involving the conductor I6. The greater part of thecurrent reaching junction il continues through the contact 2 l, switchelement 2l), and conductor 33 through the coil of the first describedrelay A, the current continuing on through conductor 34, the resistanceheater t and conductor 35 to the terminal h8 of the igniter hl, theother terminal h9 of the igniter being grounded through a conductor 36.It may be explained that a relatively heavy current is required tooperate the relay A and cause it to move a switch element intoengagement with a contact 4I that joins the previously mentionedconductor 34. When the relay A is energized it closes a circuitincluding the contact 4I, whereupon current will iiow through aconductor i2 to its junction 43 with a conductor 2l. This conductor isrepresented as including a resistance 3l, which as designated on thedrawing, is symbolic of a distributed resistance in the circuit whereofsaid conductor is a part. Accordingly, a relatively small amount of thecurrent passing relay A will reach the conductor 21 through the pathjust described-that is to say, by way of the contact 4I, element 40 andconductor 42 to junction 43. From junction 43 a part of the current willgo in one direction through the conductor 21 to a contact 28, and thencethrough the thermosensitive element t2 and a conductor 29 to the coil p3of the electromagnetic operating means of the pump P and thence to theground through a conductor 3i). The remainder of the current reachingjunction 43, will momentarily pass in the other direction through theconductor 21, past junction 26, through the coil of the relay V3,conductor 25, contact I2, circuit closing element I0 and conductor i9lto the ground. This will result in the relay V3 operating to close thecircuit between the contact 45 and element 46, thereby to eiect a flowof the current supplied to the pump operating means through a pathdescribed as follows: from junction I4, through a conductor 50, toelement 46 and thence through contact 45, conductor 2l, thermostaticelement t2 and conductor 29 to the coil p3 of the pump and on to theground through the conductor 36. A part of the current flowing fromjunction I4 will flow past junction 25 through the coil of the relay V3and, through a path already described, to the ground, thereby tomaintain the relay V3 energized and, as a consequence, the circuitclosing element 45, in engagement with the contact 45. Thus, it will beseen that, when this point in the operation of the system is reached therelay V3 will serve to lock in the pump circuit, and this condition willcontinue so long as the system is in operation. It will be understoodthat the impedance, as symbolized by the resistance 3l, of the circuitrepresented by conductor 50, the conducting element 46 and contact 45 ofrelay V3, conductors 2l and 42, and the conducting element 4i) andcontact 4I of relay A (which circuit is closed when the relay A isenergized), is of sufficient magnitude as compared to the impedance ofrelay coil A to prevent that current necessary for the continuedenergization of relay A from being diverted through said circuit andshort circuiting said coil.

Remembering that We are still concerned With the starting phase of theoperation, with the conducting element C10 of the control head switch csin engagement with the contact C14, due to the fact that thethermostatic tension element C24 is cold, so to speak, the igniter h7 issupplied with current through the ignition circuit already described.Now, with the pump operating to supply fuel to the combustion device h5,and with the igniter hr1 energized, the latter will vaporize and ignitethe fuel and start the combustion device in operation, provided thatconditions are normal.

At this point it may be explained that there is an advatnage insupplying a limited amount of air to the combustion device h5 during thestarting phase. Such amount, however, should be much less than thatrequired during the normal operating phase. Consequently, I desire toprovide a circuit for supplying a limited amount of current to this`Acombustion fan motor y" at the time the igniter hl is energized.Therefore, I include a circuit represented in part by a conductor 5Ithat leads from conductor 33 to one terminal of a resistance element 52,the other terminal of which is connected, through a conductor 53, to oneof the binding posts `of the combustion fan motor f', the other bindingpest of which is grounded through a conductor 54. The conductor 53 alsoelectrically connects the combustion fan motor f with the contact C15 ofthe control head switch e8. Intermediate the point at which theresistance element 52 has connection with the conductor 53 and thecombustion fan motor, a signal circuit branches from the .conductor 53which is represented by a conductor 55, an incandescent lamp 56, and aconductor 51 that leads to the ground.

Accordingly, during the starting phase, a limited amount of currentflows through the conductor l, past the resistance element 52, and byway of conductor 53, through the combustion fan motor, and on to theground, causing the fan motor to turn relatively slowly and supply adraft of air to the combustion device which will aid in initiatingcombustion. At the same time, this condition wil be indicated by a Weakglow of the lamp 56.

With combustion under way, the products will rise into the combustionchamber and pass out through the flue of the heat exchanger h' and onthrough the passage provided by the elbow c4. The heat imparted underthese conditions to the thermostatic tension element C24 will cause saidelement to expand and lengthen suiiciently to relax the pressure of thelever C18 on the plunger 016-, thereby to permit the conducting elementC of the switch o8 to shift from contact 014 to contact, C15, thusinterrupting the flow o1 current through the circuit represented in partby the conductor le and including the coil of the relay A.Deenergization of this relay causes withdrawal of the circuit closingelement 4G from the contact 4| which opens the ignition circuit. Openingof the aforesaid circuit also deprives voltage relay V2 of c-urent,resulting in thev Withdrawal of element 2U. from contact 2l of saidvoltage relay. Although deenergization of the relay A causes withdrawalof the circuit closing element ll from the Contact 4I, this has noeffect upon the supply of current to the pump, due to the fact that thepump circuit is locked in by the relay V3, as previously described.

Therefore,` the pump will continue to supply fuel to the combustiondevice, and to meet the demands of normal operation, the motor of thecombustion. fan F wil be operated at full speed by current now suppliedfrom conductor l5,

through conducting element c1 of the switch c5',

contact. C and conductor 53. rIhe fact that the fan is now operating atfull speed will be indicated by abrilliant glow of the lamp 5S, to whicha greater amount of' current is. now supplied from the fan circuit.

Thenal or shut-down phase ofV operation of the control system may beeffected manually by opening the switch S, or it may result from theopening of the thermostatic switch R caused by a rise, to a given value,of the temperature to which said thermostatic switch is subjected. Uponthe opening of the auxliary circuit at either of these points, the relayV is deenergized'- This resultsin the. circuitV closing element L'liwithdrawing from the contacts Il and I2'. The breaking of ther circuitincluding the last mentioned corrtact causes deenergization of the relayV3. This results in the opening of the pump circuit. by the withdrawalof the switch element e5 from the contact 45. Consequently, thecombustion device n.5 will be deprived of fuel, excepting for that whichremainsin the device at the time` the pump circuit is interrupted. Inorder that this remaining` fuel may be consumed without creating a smokycondition and the formation of an undue amount of carbon, it isnecessary to keep the combustion fan running until said fuel isconsumed. This is automatically brought about by the fact that thethermostatic tension element c24k remains heated so long as combustionprevails, and, therefore, in sufficiently relaxed condition to leave theconducting element C10 of the switch o8 in engagement With the contact015. It is through this contact that current is supplied to the motor fof the fan for normal operation of the latter. When the fire dies outand the heat subsides and the thermostatic tension element C24 cools andcontracts and thus recovers its former tension, it will function,through the intervention of the lever 018 and plunger C16, to shift theconducting element c1 from contact C15 to contact C14, thus conditioningthe system for a subsequent operation.

During the foregoing description of the cycle of operation of theheating apparatus and its control system, it has been assumed that allconditions are normal. There are times, however, when abnormalconditions occur, as will hereinafter be explained, when the systemfunctions to safeguard the apparatus and associated parts from injuryunder these abnormal conditions. Such abnormal conditions may consist offailure of the fuel to ignite; the lack of fuel, or a short circuitanywhere in the system.

In the event the fuel in the combustion device fails to ignite,prolonged flow of current through the ignition circuit will build upsufficient temperature in the resistance element t of thetimetemperature cutout switch T to cause the thermosensitive element t2thereof to withdraw from the contact 28., thus interrupting the pumpcircuit at this point and preventing ooding of the combustion devicewith fuel. If this condition prevails for any appreciable length oftime, as for exam-ple, four or five minutes, suicient heat 'will buildup in the resistance element o of the cutout O to cause thethermosensitive element o2 thereof to withdraw from the contactwherewith it normally engages. The element o2 will be held out ofengagement with said contact by the latch o3, even after said elementcools and until an opportunity is afforded to correct the conditionsresponsible for the present failure. After correction of such conditionsthe latch o3 may be released to allow the circuit to close at the cutoutO, thereby to place the system in condition for a repetition of thestarting phase, it being understood. that, upon cooling due todecnergization of the resistance element t', the thermosensitive elementt2 resumed normal condition and closed the pump. circuity at the contact23.

.In case the supply of fuel to the combustion device stops from anycause during a normal operating phase, the fire will go out and the:ierinostatic tension element c24J will cool and contract wd, throughits operative connections with the control switch es, shift theconducting element C10 of the latter out of engagement with the con-tactC15 and into engagement with the contact cli, thus conditioning thesystem for a starting phase of operation. Naturally, if the cau-sel ofthe trou-ble is not removed, the heating apparatus will fail. tofunction and conditions of the system will remain unchanged untilsuicient heat builds up in the` resistance element o to cause thecutout` to open the circuit in the mannel1 already described. Likewise,if a short circuit occurs in the system, the cutout O will function inthe manner stated to shut down the system.

I-n. case the thermostatic tension element 024 breaks during a normaloperating phase, the heating apparatus and system will continue tooperate in a normal way until the auxiliary circuit is opened, either atswitch S, or at the thermostat R; but, under these conditions, while theblower will continue to run with the advantageous effect of thoroughlypurging the combustion apparatus of gases before it can be reignited,the system will not operate automatically to reestablish the ignitionand pump circuits until the broken thermostatic tension element isreplaced.

Having thus described my invention, what l claim is:

1. In an electric control system for a liquid fuel combustion device,means governing the supply of fuel to said device, an electric actuatorfor said means, an electrical igniter for the combustion device, an airim`^eller for supplying combustion air to the device, an electric motorfor driving said impeller, a source of direct electric current, acircuit closing instrument, an electric control-unit switch having twocircuit closing positions represented, respectively, by a iirst contactmember and a second contact member and characterized by a conductingelement movable alternately into engagement with one and the other ofsaid members, a rst circuit closing relay involving two circuit closers,a second circuit closing relay, a third circuit closing relay, and afourth circuit closing relay, each relay comprising an energizing coiland a circuit closer; a main circuit including said source, saidconducting element of the control unit switch and the first contactmember thereof, the circuit closer of the second relay, the coil of thethird relay, and the igniter; an auxiliary circuit, branching from themain circuit between said source and the controlunit switch andincluding said circuit closing instrument and the coil of the rst relay,and energizable by said source of current; a branch circuit alsoenergizable by said source of current and leading from the main circuitbetween the first contact of control-unit switch and the circuit closerof the second relay and including the coil of the second relay and onecircuit closer of the first relay; a second branch circuit energizableby said source of current and including the second circuit closer of thefirst relay, the coil of the fourth relay, and the actuator of the fuelsupply means; a shunt between the main circuit, at a point intermediatethe coil of the third relay and the igniter, and the second branchcircuit, at a point intermediate the coil oi the fourth relay and thefuel supply means, and including the circuit closer of the third relay,and through which shunt said second branch circuit is first energized; asecond shunt between the second branch circuit, at a point intermediatethe coil oi the fourth relay and the last named point, and the maincircuit at a point in the latter between its junction with the auxiliarycircuit and the control-unit switch and including the circuit closer ofthe fourth relay, and through which second shunt the second branchcircuit is supplied with current after the first mentioned shunt isopened; a circuit leading from the second contact member of thecontrol-unit switch and including the electric motor of the airimpeller, and a thermostat subjected to the heat of the combustiondevice and having operative connection with the conducting element ofthe controlunit switch for causing said element to move out ofengagement with the rst contact member of said switch and intoengagement with the second it? contact member thereof when saidthermostat is heated.

2. An electric control system comprising the combination and arrangementof parts dened by claim l, and, in addition thereto, a circuit leadingfrom the last mentioned circuit at a point between the second contactmember of the control-unit switch and said motor to a point in the maincircuit intermediate the circuit closer of the second relay and the coilof the third relay, and a resistance element included in the lastmentioned circuit whereby the motor is caused -to operate at relativelylow speed while the igniter is energized.

3. An electric control system comprising the combination and arrangementof parts defined by claim l, and, in addition thereto, a thermostaticswitch in the second branch circuit serving, when cold, to maintain saidcircuit closed, and an electrical resistance heate;x in the main circuitin heating relation to said thermostatic switch to actuate saidthermostatic switch after the igniter has been energized for a givenperiod of time.

4. ln an electric control system for a liquid fuel combustion device,means governing the supply of fuel to said device, an electric actuatorfor said means, an electrical igniter for the combustion device, asource of direct electric current, a circuit closing instrument, anelectric controlunit switch including a contact member and a conductingelement movable into and out of engageznent with said member, a firstcircuit closing relay involving two circuit closers, a second circuitclosing relay, a third circuit closing relay, and a fourth circuitclosing relay, each relay comprising an energizing coil and a circuitcloser; a main circuit including said source, said conducting element ofthe control-unit switch and the contact member thereof, the circuitcloser of the second relay, the coil of the third relay, and theigniter; an auxiliary circuit, branching from the main circuit betweenthe source and the control-unit switch and including said circuitclosing instrument and the coil of the iirst relay, and energizable bysaid source of current; a branch circuit also energizable by said sourceof current and leading from the main circuit between the control-unitswitch and the circuit closer of the second relay and including the coilof the second relay and one circuit closer of the first relay, a secondbranch circuit energizable by said source of current and including thesecond circuit closer of the rst relay, the coil of the fourth relay,and the actuator of the fuel supply means; a shunt between the maincircuit, at a point intermediate the coil of the third relay and theigniter, and the second branch circuit, at a point intermediate the coilof the fourth relay and the fuel supply means, and including the circuitcloser of the third relay, and through which shunt said second branchcircuit is first energized; a second shunt between the second branchcircuit, at a point intermediate the coil of the fourth relay and thelast mentioned point, and the main circuit at a point in the latterbetween its junction with the auxiliary circuit and the control-unitswitch and including the circuit closer of the fourth relay, and throughwhich second shunt the second branch circuit derives current after theiirst mentioned shunt is opened.; and a thermostat subjected to the heatof the combustion device and having operative connection with theconducting element of the control-unit switch for causing said elementto withdraw from the contact member of said switch when said thermostatis heated.

V5. In an electric control system fora liquid `Jfuel combustion device,means governing the zsupply of fuel to said device, .an electricvactuator for said means, an electrical igniter for the combus- .tiondevice, a source of direct electrical energy, .a control-unit switch, a.thermostat subjected to the .heat of the combustion device and 'havingoperative connection with said switch, three relays, each comprising anlenergizing coil vand a circuit closer, a main circuit including saidsource, said switch, the circuit closer of the rst relay, the coil Iofthe second relay, and vsaid igniter; a branch circuit energizable bysaid source of energy and leading from the main circuit in advance ofthe circuit closer of the first relay and including the coil of saidfirst relay; Va second branch circuit energizable by said source ofenergy and leading from the main-circuit intermediate said source andthe control-unit switch and including the circuit closer of the thirdrelay and the aforesaid actuator, a further circuit energizable by saidsource of energy and leading from the second branch circuit between thecircuit closer .of the third relay and said actuator and including thecoil. lof sai-d third relay, and a shunt between the main circuit, at apoint intermediate the coil of the second relay and the igniter, and thesecond branch circuit at a point intermediate the circuit closer of thethird relay and said actuator, said shunt including the circuit-closerof said second relay, the thermostat, when heated, causing thecontrol-unit switch to open.

6. In an electric control system for use with a liquid fuelcombustiondevice, electrical means for supplying fuel `to said device,an electrical igniter for the device, a control-unit switch, athermostat subjected to the heat of the combustion device, operativeconnections between said thermostat and said switch, the switch beingclosed when the thermostat is cool and open when the thermostat isheated, a source of direct electrical energy, a main circuit includingsaid source and separating into a first branch and a second branch, arelay comprising a ycoil and a circuit closer., the first branchincluding said switch, the coil of said relay, and the igniter, thesecond branch including the fuel supply means, a shunt .between thefirst and second branches from a point in the first branch intermediatethe igniter and the coil of said relay to a point in the second branchon the source side of the fuel supply means, .and including the circuitcloser of said relay, the relay coil in the first .branch serving, whenenergized, to hold said circuit closer of .the relay .in circuit closingposition, a second vcircuit closer in the second branch between theshunt and the main circuit and having an associated electrical means foractu-ating it, said latter electrical means being in a leg from thesecond branch that is in parallel circuit relation with said fuel supplymeans and that leads from a point in said second branch between thesecond circuit closer and the .shunt and serving to maintain the secondbranch closed after the aforesaid switch is opened by the thermostat inresponse to heat generated by the combustion device.

7. In a direct current electric control system for use with a liquidfuel combustion device, a source of -direct electric current, anelectrical actuator for effecting the delivery of fuel to said device,an electrical igniter for the combustion device, an air impeller forsupplying combustion air to said device, an electric motor for operatingsaid impeller, an electric control-unit switch having two circuitclosing positions represented, respec- 12 tively, by a first contactmember and a second contact member and characterized by a conductingelement movable alternately into Yengagement lwith one and the other ofsaid members, a thermo'stat lsubjected to the heat of the 'combustiondevice, operative "connections between said thermostat 1and Vsaidconducting element, the latter being in engagement with therst contactmemiber when the Vtl'iermostat 'is cold and in engagement with thesecond contact member when the thermostat is heated, fan 'electriccircuit energizable by said source of current and including the 'firstcontact ymember of said switch and the igniter, a second electriccircuit energizable by said source of current and including the othercontact member Kof said switch land said electric motor, a Arelativelyhigh Vresistance circuit leading from a junction 'with the Afirst4mentioned circuit intermediate said rst contact merriber and theigniter to a junction with the second circuit intermediate said iot'hercont-act member and the :electric fmotor, 'said 4high resistance circuitbeing energizable by said ysource oi current, and :an- -other electriccircuit in Aparallel circuit relation 'with said control-unit switch and-energizable by :said 'source land including the :aforesaid electricalactuator.

8. An electrical control system comprising the `combination andarrangement lof parts donned by claim 7, and, in addition thereto, -aiur-ther electric Vcircuit energizable by said lsource of current andbranching 'from the -second circuit intermediate Vsai-d junction and themot-cr, .and yan :electrical indicator yin said vfurther circuit for'indicating the vstrength 'of the current flowing therethrough.

9. In an electric :control system for use with a liquid fuel combustiondevice, electrical lmeans for supplying fuel to 4said device, anelectrical igniter for the device., an :air `impeller vfor supplyingycombustion air to the device, an electric motor for drivinglsa-idiirnpeller,:a control-unit switch having two circuit closingpositions represented, respectively, by a i'lrst contact member and asecond contact member 4and characterized by -a conducting elementmovable alternately into Aengagement with one and the other of said4contact members, a lthermostat subjected to .the heat of the combustiondevice, operative connections betweensaid thermostat and the conductingelement of said control-unit switch, ,said'conducting element engagingthe iirst contact member when the thermostat is cool and `.the secondcontact member when the thermostat is heated, a source of electricalenergy, a first circuit closer, a second circuit closer, a nrstfelcctni'cal means and a second electrical means which serve, whenindividually energized, to hold the respective .circuit closers incircuit closing position, :a main circuit including said sourceandseparating into a first branch and `a second branch, the rst branchincluding said conducting element, the first contact member of said.control-unit switch., `the :first electrical means and the igniter, the,second branch leading from the main circuit .in advance of thecontrolunit switch and including the secondcircuitcloser and the fuelsupply means, a `shunt including said rst circuit closer and extendingfrom the first ybranch at A'a point :intermediate 'the iirst electricalmeans and the igniter to the second branch intermediate the secondcircuit `closer and the fuel supply means, said second electrical meanshaving electrical connection with the second fbranch at apoint in thelatter .intermediate the second circuit closer and the junction of saidshunt with the second branch, whereby said second electrical means isirst energized by current supplied thereto through said shunt andthrough the intervening part of the second branch, and, upon theshifting of the conducting element of the control-unit switch from therst contact member to the second contact member in response to theaction cf the thermostat when heated, is thereafter maintained energizedby current supplied from the main circuit through the second circuitcloser, and a further circuit energizable by current from said sourceand including the second contact member of the control-unit switch andthe electric motor of the impeller.

ALLEN E. CLEVELAND.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date Booth Dec. 4, 1928 DeLancey Nov. 19, 1935 Pagano June 15, 1937Kriechbaum Feb. 15, 1938 Bergey Aug. 8, 1939 Brace Oct. 3, 1939 MasonSept. 9, 1941 Taylor Sept. 15, 1942 Fox Sept. 25, 1945 Hall May 7, 1946Cleveland Mar. 14, 1950 Collins et a1 June 27, 1950

